1. Field of the Invention
This invention relates generally to multiple clock switching circuits and more particularly to switching circuits for selectively switching between multiple asynchronous or synchronous clocks.
2. Description of the Prior Art
Typically, a system requiring the selective switching between multiple asynchronous and synchronous clock signals utilizes independent circuits to switch, either manually or otherwise, each clock into the system. A disadvantage of the prior art is the generation of excessively brief timing pulses which can produce an unknown state within the clock drive circuitry immediately following switching between asynchronous clocks. As a result, a reinitialization is generally required before a valid state can be obtained using the new clock. Usually, a reinitialization of the clock driven circuit results in a considerable delay before valid data is realized at the driven circuit's output. A further disadvantage of the prior art occurs when the clock driven circuit is reinitialized and the circuit's previous logic state is thereby lost.